[Labs-l] Query optimization

[Huji Lee]

I am trying to find a list of those categories on EN WP that are highly
used (more than 100 subpages or subcats) but don't have a counterpart in FA
WP. The query I used is shown below and also on
https://quarry.wmflabs.org/query/7943 and is extremely slow.

Any thoughts on how to make it more efficient?

select page_title, ll_title, count(cl_to) as CNT
from page
left join langlinks
on ll_from = page_id
and ll_lang = 'fa'
join categorylinks
on page_title = cl_to
where page_namespace = 14
and ll_from is null
group by cl_to, ll_title
having CNT > 100
order by CNT desc;
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